The present invention relates to an airbag retainer for housing an airbag for protecting a vehicle occupant and the like, and more specifically, it relates to an airbag retainer having advantages of reduced cost and weight, and so on.
Most of conventional passenger vehicles are equipped with at least one airbag assembly, such as a driver airbag, a passenger airbag and a rear-seat airbag, as well as a side airbag in order to protect passengers in the event of a vehicle collision. A typical airbag assembly is mounted in a vehicle as a module incorporating a bag, a retainer, an inflator, a cover and so on.
Regarding a passenger airbag assembly as an example, a known art of the airbag assembly will be described. FIG. 10(A) is a side sectional view illustrating an example of a known passenger airbag assembly which is mounted on a board. FIG. 10(B) is a plan view illustrating the interior of a retainer of the airbag assembly in FIG. 10(A). FIG. 10(C) is a side sectional view illustrating in further detail another known passenger airbag assembly.
An airbag assembly 100 is placed in a position so as to face a windshield F mounted above an instrument panel P of a vehicle as shown in FIG. 10(A). The airbag assembly 100 has a retainer 110, wherein a cover 120, which is brought into alignment with the instrument panel P, is fixed by using cover-fixing portions 121. With this arrangement, the retainer 110 is welded at the bottom thereof to a bracket 114. A bag 103 and an inflator 105 for feeding gas into the bag 103 are arranged in the retainer 110. The bag 103 is folded and housed in the retainer 110 under normal conditions.
The retainer 110 includes a box-shaped main unit ill with a bottom and flange surfaces as shown in FIGS. 10(B) and 10(C) for better understanding. The main unit 111 has a solid structure made of metal or resin and a plurality of fixing plates 113, which engages the cover-fixing portions 121, at the mouth edge of the main unit 111. An engagement opening 110a for the inflator 105 is provided to open at the bottom of the main unit 111. A bag plate 115 integrally formed of a semicircular portion 115a and a plurality of flange portions 115b is arranged in the main unit 111. The semicircular portion 115a of the bag plate 115 holds the inflator 105. Bolts 119 fix the flange portions 115b of the bag plate 115 to a flange surface of the retainer 110. The end of an opening of the bag 103 is put between the flange portion 115b and the flange surface of the retainer 110 in a state such that the bag plate 115 is fixed to the retainer 110.
With this airbag assembly 100, the gas in the inflator 105 is introduced into the bag 103 in the event of a vehicle collision. Subsequently, the bag 103 breaks the cover 120 by tearing a tear line 122 thereof, and inflates in front of a passenger.
The retainer 110 of the above-described known airbag assembly 100 has the following problems because of its solid structure made of a metal or resin.
(I) Retainer Made of Metal
(1) A metal retainer is formed by deep drawing or sheet metal welding. Because of its poor formability as compared to sheet metal welding, deep drawing is unsuitable for forming a metal sheet into a complicated shape. Sheet metal welding, on the other hand, requires an increased number of manufacturing processes for welding, resulting in increased cost.
(2) Metal retainers are heavier than resin retainers.
(II) Retainer Made of Resin
(3) Attaching a fixing bracket made of metal to a main unit of a resin retainer after the main unit has been molded requires an increased cost. The main unit and the fixing bracket therefore are often formed in a single-piece manner. This single-piece structure, however, does not allow only one type of a retainer to be used for plural types of vehicles, each having a different bracket (see the bracket 114 in FIG. 10(A) as an example). Therefore, the resin retainer requires a new metal mould for producing a whole retainer, even though the only difference between them resides in the shapes of the fixing brackets. This limits the range of usage of the resin retainer.
(4) only compressed-gas type inflators are appropriate for the resin retainers, because the portions of the retainers coming into contact with inflators may melt due to heat generated when the inflators are ignited.
(5) Two types of inflators are available, i.e. a compressed gas type and a combustion gas type, and an appropriate one is chosen. In the meantime, as to the inflator of the compressed gas type, little change in temperature occurs in the inflator body upon activation, as compared to that of the combustion type. Because of the reason as mentioned in (4), an inflator of the compressed gas type is usually an only choice.
(6) A resin retainer requires a thicker plate than a metal retainer does in order to obtain the same strength. Specifically, the thickness of a resin plate must be three times or more greater than that of a metal plate while the thickness of about 1 mm is sufficient for the metal plate, thereby rendering it difficult to downsize the resin retainer.
In view of the above-described problems, the object of the present invention is to provide an airbag retainer having advantages of reduced cost, weight, and size.
Further objects and advantages of the invention will be apparent from the following description of the invention
To solve the above-described problems, an airbag retainer of the present invention, for housing and holding an airbag which inflates in an emergency and an inflator which supplies gas for inflating the airbag, comprises a bag-housing member (an upper portion: an upper retainer) made of a resin, and an inflator-holding member (a lower portion: a lower retainer) made of metal.
The airbag retainer according to the present invention has an improved formability, and can achieve the reduced production cost and weight, as compared to a solid metal retainer. When comparing with a solid resin retainer, because of the increased heat endurance strength of the inflator-holding member, an inflator in a wider range of types is available for the airbag retainer. In addition, the above increased strength permits the inflator-holding member to reduce its thickness, accordingly allowing the retainer to reduce its height.
When the airbag retainer of the present invention is applied to a plurality of different types of vehicles, the only thing to do is to choose a usable bracket, which is to be spot-welded to the lower retainer, according to a vehicle type. This renders the airbag retainer suitable for a wider range of uses. Welding the bracket to the lower retainer is a known fixing art as has been used for conventional retainers.
According to the airbag retainer of the present invention, the upper retainer may have a frame-shaped structure provided with sidewalls on the four sides thereof, and the lower retainer may have sidewalls on a pair of opposing sides among its four sides, such that the sidewalls of the lower retainer partly overlap the corresponding sidewalls of the upper retainer.
This structure serves to enhance the strength against an expansive force of the inflating bag, thereby to prevent a fish-mouth deformation of the retainer. The fish-mouth deformation means a state in which the central portions of the sidewalls of the lower retainer are deformed outward upon receiving the expansive force of the inflating bag.
Also, according to the airbag retainer of the present invention, the upper retainer and the lower retainer may have a plurality of fastening portions. At least one of the plurality of fastening portions is preferably broken or stretched when a load is applied to an instrument panel of an automobile.
Further, according to the airbag retainer of the present invention, a plurality of flange-shaped fastening portions of each of the upper retainer and the lower retainer is preferable arranged to have surface-to-surface contact with each other. At least one fastening portion of the upper retainer among the plurality of fastening portions is preferably arranged to underlie the corresponding fastening portion of the lower retainer.
The metal lower retainer bears a tension of the inflating bag on its flange surfaces, thereby serving to provide enough strength of the airbag retainer. When a passenger hits his head against an instrument panel, on the other hand, the resin upper retainer is easily deformed because of less constraint in the downward direction. With this arrangement, the lower retainer can be built to the upper retainer from either above or below.
Still further, according to the airbag retainer of the present invention, each of the plurality of fastening portions of the upper retainer may have a notch or depression formed thereon. The depressed portion is thinner than other portions of the same fastening portion. When a passenger hits his head against an instrument panel P, accordingly, the fastening portion is likely to be sheared or deformed at the depression.
Yet further, according to the airbag retainer of the present invention, a protrusion is preferably formed on a sidewall of the lower retainer. When a passenger hits his head against the instrument panel, the upper retainer is pushed from the upper mouth thereof. With this pushing force, the upper retainer is deformed from its top, and moved downward to hit the protrusion of the lower retainer. That is, the sidewall of the upper retainer pushes down the sidewall of the lower retainer from above.
According to the airbag retainer of the present invention, the sidewall of the upper retainer, which overlaps the corresponding sidewall of the lower retainer, may have a window formed by cutting away the lower part of the sidewall. Also, an outer surface of the sidewall of the lower retainer is preferably exposed outward at the window.
For attaching a vehicle-mounting bracket (bracket for mounting an airbag module on an internal frame of a vehicle body) to the side wall of the lower retainer, the window of the sidewall of the upper retainer serves to provide a wide area where the side wall of the lower retainer is exposed outward, thereby rendering a variety of vehicle-mounting brackets available.
When the material costs of resin and metal for the same area are compared, the resin costs about three times of metal. According to this embodiment of the present invention, the window formed in the sidewall serves to reduce the quantity of resin used, leading to achieve the reduced cost.
Still yet further, according to the airbag retainer of the present invention, a plurality of reinforcement portions is preferably provided along the edges of an upper mouth of the upper retainer. With this construction, the plurality of reinforcement portions serves to suppress the deformation of the upper retainer caused by a load of the inflating bag.
Furthermore, according to the airbag retainer of the present invention, the upper retainer may have the upper mouth wider than the lower mouth. With this configuration, a plurality of retainers can be stacked, thereby requiring less space for transportation or inventory.
Still furthermore, an airbag retainer of the present invention is used for housing and holding an airbag that inflates in an emergency, and an inflator that supplies gas for inflating the airbag. The airbag retainer comprises a bag-housing member (upper retainer) which is made of steel or light metal containing at least one of magnesium and aluminum, and an inflator-holding member (lower retainer) which is made of metal. A plurality of flange-shaped fastening portions of the upper retainer and the lower retainer is arranged to have surface-to-surface contact with each other. At least one fastening portion of the upper retainer among the plurality of fastening portions is arranged to underlie the corresponding fastening portion of the lower retainer.